Background/Purpose Down syndrome is a genetic disorder resulting in gene over-expression causing over 80 clinical features occurring more frequently in this population than the population at large. Features such as short statures, hypoactive thyroids, and cardiac abnormalities collectively make the relationship between physical activity and body composition challenging to understand.
Method 32 individuals (17 typical development; 15 Down syndrome) 9-17 years old were assessed to determine if methods for measuring physical activity and body composition yield valid information for individuals with Down syndrome. Body composition was measured using the BODPOD and BMI percentile adjusted for age and gender. Physical activity measurements were collected with a hip-mounted accelerometer and a sub-maximal graded treadmill protocol. Heart rate and VO2 were measured using a COSMED portable metabolic cart.
Analysis/Results Due to suppressed peak heart rates associated with Down syndrome, significant differences in heart rate and VO2 were found between both groups for identical workloads. This resulted in accelerometers misclassifying intensity of physical activity for those with Down syndrome. Similarly, short statures associated with Down syndrome grossly inflated this groups BMI percentile which in turn significantly influenced the relationship between BMI and percent body fat.
Conclusions Although this population is at risk for increased weight gain and present with inflated BMIs, they might not be as sedentary as their body fat and BMIs suggest. Future directions should focus on examining these relationships in combination with other primary health indicators, specifically those associated with metabolic syndrome.